Capacitance level measurement utilises an insulated electrode and the wall of a tank assuming this wall is conductive, which constitute the two plates of a capacitor. Should the wall be non - conductive, a second probe would be required.

The variable would be the changing level in the tank which is the dielectric of the medium. This changing capacitance is converted into a current change, proportional to the level, by the electronic circuitry incorporated in the probe head.